Update to document the default validation policy (#667)
Update to document the default validation policy (#667)

See https://leastprivilege.com/2017/01/06/bootstrapping-openid-connect-discovery/
siyo-wang/IdentityServer4,MienDev/IdentityServer4,jbijlsma/IdentityServer4,IdentityServer/IdentityServer4,chrisowhite/IdentityServer4,siyo-wang/IdentityServer4,chrisowhite/IdentityServer4,IdentityServer/IdentityServer4,jbijlsma/IdentityServer4,MienDev/IdentityServer4,siyo-wang/IdentityServer4,IdentityServer/IdentityServer4,MienDev/IdentityServer4,jbijlsma/IdentityServer4,IdentityServer/IdentityServer4,chrisowhite/IdentityServer4,jbijlsma/IdentityServer4,MienDev/IdentityServer4